A known vehicle seat belt retractor comprises a spool for holding a wound length of seat belt webbing. The spool is supported for rotation in winding and unwinding directions. A spring biases the spool to rotate in the winding direction to wind up the webbing onto the spool. The spool rotates in an unwinding direction against the force of the spring when the webbing is unwound from the spool to be buckled around a vehicle occupant. After the webbing is buckled around a vehicle occupant, slack in the webbing is wound onto the spool because the spool is rotated in the winding direction by the spring. The webbing is thereafter held against the vehicle occupant by the force of the spring biasing the spool to rotate in the winding direction. A locking mechanism prevents unwinding of the webbing from the spool in order to hold the vehicle occupant from moving forward in a crash. However, forward movements of the vehicle occupant under noncrash conditions, such as to reach across the vehicle interior, are restrained by the tension in the webbing which results from the force of the spring biasing the spool to wind up the webbing.
Mechanisms for reducing tension in seat webbing are known. U.S. Pat. No. 4,026,494 discloses a comfort spring to counteract the force of a rewind spring which biases a retractor spool to wind up the webbing. One end of the comfort spring is connected to a housing for the seat belt retractor. The other end of the comfort spring is connected to a rotatable disk which carries a pawl. When the spool rotates to wind up the webbing, the spool turns a ratchet wheel connected to the spool. The ratchet wheel has teeth which engage the pawl carried on the rotatable disk. The comfort spring is then connected in opposition to the rewind spring through the rotatable disk, the pawl, and the ratchet wheel connected to the spool. The comfort spring thereby resists the force of the rewind spring biasing the spool to wind up the webbing. The resistance of the comfort spring against the rewind spring reduces the tension which the rewind spring applies to the webbing. A cam disengages the pawl from the ratchet wheel in order to disengage the comfort spring from the rewind spring after the spool rotates approximately one-half of a revolution about its axis. The comfort spring therefore reduces tension in the webbing throughout movement of only a few inches of the webbing.